Filestreaming performance issue webclient overriding

public class WebClientEx : WebClient
   {
 
       protected override WebRequest GetWebRequest(Uri address)
       {
 
           HttpWebRequest request = (HttpWebRequest)base.GetWebRequest(address);
 
           request.ReadWriteTimeout = 2147483647;
 
           request.Timeout = 2147483647;
 
           request.SendChunked = true;
 
           request.AllowWriteStreamBuffering = false;
           request.ContentType = "application/octet-stream";
           // request.exnc = Encoding.UTF8;

           return request;
 
       }
 
   }


WebClientEx wc = new WebClientEx();
 
                      wc.UploadFileAsync(new Uri(@"https://www.example.com/UploadFile.svc/UploadFile"), "POST", file);